# AP Chemistry Homework - Percentage by weight?

My AP [Advance Placement] Chemistry teacher threw this problem at me for homework... and I am so lost on where to start. Please help! TT~TT

1) A 2.000 gram sample containing graphite (carbon) and an inert substance was burned in oxygen and produced a mixture of carbon dioxide and carbon monoxide in the mole ration 2.00 : 1.00. The volume of oxygen used was 747.0 milliliters at 1,092K and 12.00 atmospheres pressure. Calculate the percentage by weight of the graphite in the original mixture.

I'm going to take a guess and say the formula for this is...

PV = nRT ?

Relevance
• Anonymous

The percent composition (percentage composition) of a compound is a relative measure of the mass of each different element present in the compound.

To calculate the percent composition (percentage composition) of a compound

* Calculate the molecular mass (molecular weight, formula mass, formula weight), MM, of the compound

* Calculate the total mass of each element present in the formula of the compound

* Calculate the percent compositon (percentage composition): % by weight (mass) of element

= (total mass of element present ÷ molecular mass) x 100